package cn.cloud.all.security.web.authentication.preauth;

import org.springframework.util.Assert;

import javax.servlet.http.HttpServletRequest;

/**
 * A simple pre-authenticated filter which obtains the username from a request header, for
 * use with systems such as CA Siteminder.
 * <p>
 * As with most pre-authenticated scenarios, it is essential that the external
 * authentication system is set up correctly as this filter does no authentication
 * whatsoever. All the protection is assumed to be provided externally and if this filter
 * is included inappropriately in a configuration, it would be possible to assume the
 * identity of a user merely by setting the correct header name. This also means it should
 * not generally be used in combination with other Spring Security authentication
 * mechanisms such as form login, as this would imply there was a means of bypassing the
 * external system which would be risky.
 * <p>
 * The property {@code principalRequestHeader} is the name of the request header that
 * contains the username. It defaults to "SM_USER" for compatibility with Siteminder.
 * <p>
 * If the header is missing from the request, {@code getPreAuthenticatedPrincipal} will
 * throw an exception. You can override this behaviour by setting the
 * {@code exceptionIfHeaderMissing} property.
 *
 * @author Luke Taylor
 * @since 2.0
 */
public class RequestHeaderAuthenticationFilter extends AbstractPreAuthenticatedProcessingFilter {
    private String principalRequestHeader = "SM_USER";
    private String credentialsRequestHeader;
    private boolean exceptionIfHeaderMissing = true;

    /**
     * Read and returns the header named by {@code principalRequestHeader} from the
     * request.
     *
     * @throws PreAuthenticatedCredentialsNotFoundException if the header is missing and
     *                                                      {@code exceptionIfHeaderMissing} is set to {@code true}.
     */
    protected Object getPreAuthenticatedPrincipal(HttpServletRequest request) {
        String principal = request.getHeader(principalRequestHeader);

        if (principal == null && exceptionIfHeaderMissing) {
            throw new PreAuthenticatedCredentialsNotFoundException(principalRequestHeader + " header not found in request.");
        }

        return principal;
    }

    /**
     * Credentials aren't usually applicable, but if a {@code credentialsRequestHeader} is
     * set, this will be read and used as the credentials value. Otherwise a dummy value
     * will be used.
     */
    protected Object getPreAuthenticatedCredentials(HttpServletRequest request) {
        if (credentialsRequestHeader != null) {
            return request.getHeader(credentialsRequestHeader);
        }

        return "N/A";
    }

    public void setPrincipalRequestHeader(String principalRequestHeader) {
        Assert.hasText(principalRequestHeader, "principalRequestHeader must not be empty or null");
        this.principalRequestHeader = principalRequestHeader;
    }

    public void setCredentialsRequestHeader(String credentialsRequestHeader) {
        Assert.hasText(credentialsRequestHeader, "credentialsRequestHeader must not be empty or null");
        this.credentialsRequestHeader = credentialsRequestHeader;
    }

    /**
     * Defines whether an exception should be raised if the principal header is missing.
     * Defaults to {@code true}.
     *
     * @param exceptionIfHeaderMissing set to {@code false} to override the default
     *                                 behaviour and allow the request to proceed if no header is found.
     */
    public void setExceptionIfHeaderMissing(boolean exceptionIfHeaderMissing) {
        this.exceptionIfHeaderMissing = exceptionIfHeaderMissing;
    }
}
